Development of sustainable porous adsorbent for cationic dye adsorption: A fresh start for waste valorization

Abstract

Industrial wastewater treatment has been a serious global issue in recent decades, and waste management necessitates the invention of new, cost-effective, sustainable technologies. There is a massive demand for potential wastewater purification methods using eco-friendly, low-cost material. Adsorption is the most affordable, reliable, and operationally quick wastewater treatment method. In the 21st century, there is a rising demand for environmentally friendly porous geopolymer adsorbents that may be produced from industrial waste via the circular economy concept. In this work, a cost effective, porous, shaped, fly-ash-based adsorbent is prepared to efficiently remove cationic dyes from wastewater. Various percentages of GGBS and clay are combined with fly ash to improve the removal efficiency of the synthesized adsorbent. Parent batches are activated using an activator solution of sodium silicate and sodium hydroxide to prepare the geopolymer slurry. To create a foamed slurry with surface tension, sodium dodecyl sulfate was added at 0.5%, 1%, and 1.5% as a foaming agent. Using the injection solidification process, the slurry was injected drop by drop into the PEG-6000 medium using a syringe. The bead-shaped adsorbents are then cleaned and dried at 60°C for 48 hours. Standard techniques (FTIR, XRF, XRD, and SEM-EDX) were used to characterize the adsorbents. Methylene blue (MB), a hazardous dye, was removed from water using batch mode to assess the adsorbents' adsorption capabilities. With a maximum adsorption capacity of 37 mg/g and a removal efficiency of 90%, the ideal geopolymer-shaped adsorbent demonstrated a high adsorption efficiency for 10 mg/L of MB dye solution (pH = 9) at room temperature. The porous beads recycle up to 8 times for multiple cycle uses. The adsorption kinetics, which follow a pseudo second-order model, emphasize how the geopolymer's unique ion exchange capabilities generally enabled it to absorb MB by chemisorption. The study examines the adsorbent's features in detail, including the regeneration and desorption processes.